An imaging nuclear survey system

A combined video and gamma ray imaging system has been developed to rapidly determine the location, distribution, and intensity of gamma ray sources. This instrument includes both a conventional video camera and a gamma ray imaging system, which is based upon a position sensitive photomultiplier tube, a scintillator, and a pinhole collimator. The gamma camera records the position and energy of each interaction, determining the energy spectrum and count rate from each direction. The design of the instrument and results of preliminary field tests will be presented. We have used a prototype of such an instrument in preliminary field tests to image radioactive sources with gamma ray energies between 120 keV and 2.4 MeV. This new system achieves an angular resolution for the nuclear image of 60 with an efficiency of 3×10^-6 at 1 meter, a performance suitable for many nuclear applications. The sensitivity of the system is sufficiently high that, in a low background environment, a 1 mCi ¹³⁷Cs source at 5 meters can be located in <30 seconds. Alternatively, higher spatial resolution can be attained at lower efficiency and longer imaging times